Fix backup performance

MatrixSDK/Crypto/CryptoMachine/MXCryptoMachine.swift

@@ -64,6 +64,12 @@ class MXCryptoMachine {
     private let syncQueue = MXTaskQueue()
     private var roomQueues = RoomQueues()
 
+    // Temporary properties to help with the performance of backup keys checks
+    // until the performance is improved in the rust-sdk
+    private var cachedRoomKeyCounts: RoomKeyCounts?
+    private var isComputingRoomKeyCounts = false
+    private let processingQueue = DispatchQueue(label: "org.matrix.sdk.MXCryptoMachine.processingQueue")
+
     private let log = MXNamedLog(name: "MXCryptoMachine")
 
     init(userId: String, deviceId: String, restClient: MXRestClient, getRoomAction: @escaping GetRoomAction) throws {
@@ -700,12 +706,14 @@ extension MXCryptoMachine: MXCryptoBackup {
     }
 
     var roomKeyCounts: RoomKeyCounts? {
-        do {
-            return try machine.roomKeyCounts()
-        } catch {
-            log.error("Cannot get room key counts", context: error)
-            return nil
+        // Checking the number of backed-up keys is currently very compute-heavy
+        // and blocks the main thread for large accounts. A light-weight `hasKeysToBackup`
+        // method will be added into rust-sdk and for the time-being we return cached counts
+        // on the main thread and compute new value on separate queue
+        processingQueue.async { [weak self] in
+            self?.updateRoomKeyCountsIfNeeded()
         }
+        return cachedRoomKeyCounts
     }
 
     func enableBackup(key: MegolmV1BackupKey, version: String) throws {
@@ -777,6 +785,23 @@ extension MXCryptoMachine: MXCryptoBackup {
         }
         return try machine.importRoomKeys(keys: string, passphrase: passphrase, progressListener: progressListener)
     }
+
+    // MARK: - Private
+
+    private func updateRoomKeyCountsIfNeeded() {
+        guard !isComputingRoomKeyCounts else {
+            return
+        }
+
+        isComputingRoomKeyCounts = true
+        do {
+            cachedRoomKeyCounts = try machine.roomKeyCounts()
+        } catch {
+            log.error("Cannot get room key counts", context: error)
+            cachedRoomKeyCounts = nil
+        }
+        isComputingRoomKeyCounts = false
+    }
 }
 
 extension MXCryptoMachine: Logger {

MatrixSDK/Data/MXRoom.h

@@ -176,12 +176,18 @@ FOUNDATION_EXPORT NSInteger const kMXRoomInvalidInviteSenderErrorCode;
 
 /**
  Indicate if the room is tagged as a direct chat.
+ 
+ @warning: This is an O(n) computed property that iterates through all
+ direct rooms to determine whether any particular room is direct.
  */
 @property (nonatomic, readonly) BOOL isDirect;
 
 /**
  The user identifier for whom this room is tagged as direct (if any).
  nil if the room is not a direct chat.
+ 
+ @warning: This is an O(n) computed property that iterates through all
+ direct rooms to determine given direct user id.
  */
 @property (nonatomic, readonly) NSString *directUserId;
 

MatrixSDK/Data/MXRoom.m

@@ -3537,12 +3537,14 @@ - (void)setReadMarker:(NSString*)eventId withReadReceipt:(NSString*)receiptEvent
 - (BOOL)isDirect
 {
     // Check whether this room is tagged as direct for one of the room members.
+    // This is an O(n) operation.
     return (self.directUserId != nil);
 }
 
 - (NSString *)directUserId
 {
     // Get the information from the user account data that is managed by MXSession
+    // This is an O(n) operation.
     return [self.mxSession directUserIdInRoom:_roomId];
 }
 

MatrixSDK/Space/MXSpaceService.swift

@@ -498,13 +498,8 @@ public class MXSpaceService: NSObject {
         let startDate = Date()
         MXLog.debug("[MXSpaceService] buildGraph: started")
 
-        var directRoomIds = Set<String>()
-        let roomIds: [String] = self.session.rooms.compactMap { room in
-            if room.isDirect {
-                directRoomIds.insert(room.roomId)
-            }
-            return room.roomId
-        }
+        var directRoomIds = Set(session.directRooms?.flatMap(\.value) ?? [])
+        let roomIds = session.rooms.compactMap(\.roomId)
 
         let output = PrepareDataResult()
         MXLog.debug("[MXSpaceService] buildGraph: preparing data for \(roomIds.count) rooms")

changelog.d/pr-1641.change

@@ -0,0 +1 @@
+CryptoV2: Fix backup performance